Process for preventing yellowing of moist raw wool through treatment with formaldehyde



United States Patent 3,282,639 PROCESS FOR PREVENTlN G YELLOWING 0F MOIST RAW WOOL THROUGH TREATMENT WITH FORMALDEHYDE Harold P. Lundgren, Berkeley, and Clay E. Pardo, Jr., Albany, Califi, assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Apr. 8, 1963, Ser. No. 271,524 3 Claims. (Cl. 8-127.6)

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to and has among its objects the provision of novel methods for protecting and preserving raw wool, particularly to prevent yellowing thereof on storage. Further objects and advantages of the invention will be evident from the following description wherein parts and percentages are by weight unless otherwise specified.

In preparing wool for the market the following procedure is conventional: The sheep are sheared at the ranch and the fleece from each animal is folded into a bundle. Ten to twenty of these bundles are stuffed into burlap bags and the bagged material is then shipped to a central location, such as a marketing organization, where the bags of fleece are stored until graded and sold by auction or other type of sale. The condition of the fleeces will vary as to moisture content according to the vagaries of the weather. For example, if the shearing is done in rainy weather the fleeces will have a relatively high moisture content and, moreover, they will retain this quality during shipping and storage because of the particular way in which they are packed. Thus, because the individual fleeces are folded into a bundle and the bundles tightly crammed into bags, there is essentially no diffusion of moisture and if the fleeces were wet when packed, they remain wet. As a consequence of being stored in a moist condition certain deleterious effects take place. A primary point is that the wool becomes yellow. This yellowing occurs quite rapidly and, for example, with fleeces of about 30% moisture content a definite yellowing is visible in a matter of two weeks storage at room temperature. As the storage time is extended the degree of yellowing is increased. This phenomenon of yellowing is of concern to the producer because yellow wool commands a lower price than white wool and is not suitable for production of light-colored fabrics, garments, etc. It is to be noted that the yellow color is not removed when the wool is subjected to conventional scouring. This indicates that the phenomenon involves a chemical reaction with the wool rather than a mere physical coating. In addition to development of a yellow color, the storage or raw wool in a damp state causes degradation of the wool. This is evidenced by the increased alkali and acid solubility of the fibers. In general, such factors as higher temperature of storage and higher moisture content will increase the rate of yellowing and degradation.

In accordance with the invention the problems outlined above are obviated by a process which involves applying to the raw woola protective agent, namely, formaldehyde 3,282,639 Patented Nov. 1, 1966 or the polymers thereof. The wool treated in this manner may be stored for long periods without developing yellowness or degradation of the fibers. Formaldehyde is available in commerce as a solution in water and in carrying out the process such solution may be sprayed or sprinkled onto the wool. Preferably, a polymer of formaldehyde, such as trioxymethylene or paraformaldehyde, is used, as these compounds are solids and can be applied more easily to the wool. Coming into special consideration is paraformaldehyde. This is a linear polymer of formaldehyde and is a solid, commercially available as a powder. This powder is dusted onto the wool and since it is applied as such no solvent is required. This also has the advantage of ease of application and avoiding the addition of moisture to the wool as necessarily occurs when aqueous solutions of formaldehyde are used. The amount of agent to be used will vary depending on such factors as the moisture content of the raw wool, the temperature of storage, and the degree of protection desired. For example, it is obvious that a larger amount of the agent will be required in a case where the wool is especially wet than one wherein the wool is drier. In general, amounts of the agent varying from about 0.1 to about 2%, by weight, based on the weight of the raw wool, are used. A particular advantage of the process of the invention is its simplicity in that the agent is applied to the raw Wool, which is then handled in the usual way. No special equipment is required and the agents in question are inexpensive and readily available in commerce. Although the procedure of the invention may be applied to raw wool in any state, it is of particular advantage where the wool is damp, i.e. where it contains more than about 20% moisture. It is obvious that in applying the invention to such damp wool, the wool is left in its damp state; no drying operations are needed.

The invention is further demonstrated by the following illustrative example:

Raw wool (Dubois fleeces, graded 64s, 1959 clip) was divided into a series of samples. All of the samples were moistened to a level of 30% or as near to this level as experimentally possible. Onesample was dusted with paraformaldehyde; others were treated with formaldehyde by carrying out the moistening with dilute solutions (1 to 5%) of formaldehyde; a last sample (control) was only moistened. All the samples were packed in polyethylene bags (to prevent loss or gain of moisture) and placed in an unlighted room where they were held at 35 C. At intervals, samples were removed, extracted with Stoddard solvent and scoured to remove grease, suint, dirt, etc. The cleaned wool was then hand carded and its percent reflectance (Rd value) and its yellownes's index (b value) were measured with a Gardner color difference meter. With this instrument, the brighter the sample, the higher the Rd value; the yellower the sample, the higher the b value. Also, after 5 weeks of storage, samples of the degreased and scoured wool were tested for acid and alkali solubility. Acid solubility was obtained by heating a dried, weighed sample of wool in a 5 N HCl solution at 65 C. for 1 hour, filtering, washing, and drying the residue and reweighing to determine loss in Weight.

Alkali solubility was obtained by heating a dried, weighed sample of wool in 0.1 N NaOH solution at 65 C. for '1 hour, filtering, washing, and drying the residue and reweighing to determine loss in Weight. tained are tabulatd below:

The results ob- 3. The process of claim 2 wherein the agent is paraformaldehyde in powdered form.

Percent Reflectance (Rd) and Yellowness Index (b) Acid Alkali solubility solubility Run Moisture Agent applied and amount thereof, Initial After 2 weeks After 5 weeks After 13 weeks (after 5 (after 5 content, percent storage storage storage weeks weeks percent storage) storage) 1 percent percent Rd b Rd b Rd b Rd 1 b 36 Formaldehyde, 0.36 61. 5 .9. 5 57. 8 11. 55.1 12.8 51. 9 f 15. l1. 3 8. 4 31 Formaldehyde, 0.93 60. 8 9. 5 60. 9 9. 9 58. 8 11. 0 57. 2 13.8 4. 5 4. 7 31 Formaldehyde, 1.55 62. 3 9. U 61. 3 4 60. 2 10. 8 59. 4 11. 2 4, 9 4, 9 30 Paraformaldehyde 1.00 62. 5 9. 6 59. 4 10. 6 59. 4 11. 2 85. 6 11. 4 3. 5 5. 2 30 None (control) 58. 2 l1. 8 52. 4 12. 5 50. 5 15. 6 49. 0 18. 9 12. 9 13. 7

1 Higher values of Rd indicate brighter samples; of b, yellower samples.

Having thus described the invention, what is claimed is:

1. In the process wherein sheep are sheared at a time when their fleece is damp, the individual damp fleeces are folded into bundles, the bundles of fleece are packed into an assembly which is substantially impervious to diffusion of moisture, and said assembly is shipped and stored, the improvement which comprises distributing on the fleeces prior to folding, an agent selected from the group consisting of formaldehyde, trioxymethylene, and paraformaldehyde in an amount about from 0.1% to 2% by weight based on the weight of fleece.

2. A process for preventing the yellowing of raw wool when stored in a damp condition which comprises distributing on the damp raw wool an agent selected from the group consisting of formaldehyde, trioxymcthylene, and paraformaldehyde in an amount about from 0.1% to 2% by weight based on the weight of raw Wool and storing said treated raw wool in its original damp condition.

References Cited by the Examiner UNITED STATES PATENTS 787,923 4/1905 Kann 8133 2,220,805 11/ 1940 Pratt et a1. 8111 2,422,586 6/ 1947 Royer et al 8133 2,676,871 4/1954 McGovern 8--133 2,880,055 3/1959 Thomson et al. 8111 NORMAN G. TORCHIN, Primary Examiner.

J. CANNON, Assistant Examiner. 

1. IN THE PROCESS WHEREIN SHEEP ARE SHEARED AT A TIME WHEN THEIR FLEECE IS DAMP, THE INDIVIDUAL DAMP FLEECES ARE FOLDED INTO BUNDLES, THE BUNDLES OF FLEECE ARE PACKED INTO AN ASSEMBLY WHICH IS SUBSTANTIALLY IMPERVIOUS TO DIFFUSION OF MOISTURE, AND SAID ASSEMBLY IS SHIPPED AND STORED, THE IMPROVEMENT WHICH COMPRISES DISTRIBUTING ON THE FLEECES PRIOR TO FOLDING, AN AGENT SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE, TRIOXYMETHYLENE, AND PARAFORMALDEHYDE IN AN AMOUNT ABOUT FROM 0.1% TO 2% BY WEIGHT BASED ON THE WEIGHT OF FLEECE.
 2. A PROCESS FOR PREVENTING THE YELLOWING OR RAW WOOL WHEN STORED IN A DAMP CONDITION WHICH COMPRISES DISTRIBUTING ON THE DAMP RAW WOOL AN AGENT SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE, TRIOXYMETHYLENE, AND PARAFORMALDEHYDE IN AN AMOUNT ABOUT FROM 0.1% TO 2% BY WEIGHT BASED ON THE WEIGHT OF RAW WOOL AND STORING SAID TREATED RAW WOOL IN ITS ORIGINAL DAMP CONDITION. 